The 3rd Generation Partnership Project (3GP) Long Term Evolution (LTE) and the Institute of Electrical and Electronics Engineers (IEEE) 802.16m are being developed as candidates of a next-generation wireless communication system. The 802.16m standard involves two aspects: continuity of the existing IEEE 802.16e standard and the future standard for a next-generation IMT-Advanced system. Thus, the 802.16m standard is required to meet advanced requirements for the IMT-Advanced system while maintaining compatibility with a mobile WiMAX system based on the IEEE 802.16e standard.
A wireless communication system generally uses a single bandwidth to transmit data. For example, a 2nd-generation wireless communication system uses a bandwidth of 250 kHz to 1.25 MHz, and a 3rd-generation wireless communication system uses a bandwidth of 5 MHz to 10 MHz. In order to support an increasing transmission capacity, recently, the next-generation system continues to extend a bandwidth of 20 MHz or larger. It is inevitable to increase the bandwidth in order to improve the transmission capacity, but the support of a large bandwidth may cause much power consumption in case where the required quality of service is low.
Thus, a multi-carrier system emerges to transmit and/or receive data in a wideband through multiple carriers. A carrier is defined by a center frequency and its bandwidth. For example, if a single carrier corresponds to a bandwidth of 5 MHz, a bandwidth of a maximum 20 MHz can be supported by using four carriers.
The use of the plurality of carriers needs a method for effectively obtaining or maintaining synchronization of the carriers. Ranging is one of methods for obtaining uplink synchronization in the IEEE 802.16 standard. During the ranging, a mobile station obtains or maintains uplink synchronization by adjusting an uplink transmission parameter.
The ranging may be performed for every carriers. However, if the number of available carriers increases, the ranging may be delayed and power consumption may increase.